Modern fixed wing commercial transport aircraft share features in common with their predecessors, including wings, a fuselage, control surfaces and engines. Continuous advancement in aerodynamics, materials, engine power and efficiency, and component design contribute to faster, safer air travel. However, the generally cylindrical fuselage has remained a fairly consistent and recognizable feature of commercial aircraft.
An aircraft fuselage is typically divided into separate volumes. In many instances, passengers sit in a volume referred to as the passenger cabin. The passenger cabin is often separated from volumes below the passenger cabin in which cargo is carried, in which airplane mechanical and electrical systems are located, and through which air flows. The cargo volumes may be axially separated by the wing box and main landing gear bay into the forward and aft cargo compartments. The combination of the passenger cabin and crown volumes is commonly referred to as the upper lobe, while the combination of the cargo compartments, bilge, left and right cheeks, and floor beam volumes is commonly referred to as the lower lobe.
Conditioned air is provided to the passenger volume to pressurize the airplane fuselage and control temperature, contaminants and odors. The majority of the air (air not transported directly to the lower lobe by the air moving system) must flow from the upper lobe to the lower lobe of the fuselage where it can either be recirculated back to the passenger cabin or be released to the ambient atmosphere from which it was originally drawn. Transport of air flow from the upper to lower lobes is intended to occur through return air grilles located near the interface of the floor and passenger cabin sidewalls.
“Sidewall air flow” or “SWF” is a term used to describe unintended air flow from an aircraft upper lobe to lower lobe via unintended paths. These unintended air flow paths include, but are not limited to, the sidewall cavity between the airplane skin and the passenger cabin sidewall liner panel and the volume between the aft pressure bulkhead and the aft cabin galley endwall. This air leakage may impact performance of aircraft systems, including impacting the passenger cabin Return Air Grille (RAG) air velocity, which affects the smoke penetration performance during a cargo fire event, the thermal performance of the Cabin Air Conditioning and Temperature Control System (CACTCS), the ability of the ECS subsystem to prevent smoke and odor migration, such as that discharged by the Lavatory and Galley Ventilation (LGV) subsystem below the cabin floor, into the passenger cabin, the pressure differential and resultant air flow direction between the Flight Deck (FD) and passenger cabin, and the efficiency with which the Air Distribution (AD) subsystem ventilates the passenger cabin.
It has been supposed that the various components housed in the space within the fuselage wall structure, i.e. the “wall volume,” that are often packed quite tightly, sufficiently obstructed air flow within the wall volume. However, despite the presence of tightly packed wall volume components within the wall volume, undesired air flow within the wall volume continues to occur.
Accordingly, those skilled in the art continue with research and development efforts aimed at reducing air leakage beyond intended air flow paths in an aircraft.